Automatic damper



May 26, 1931. w. D. LUCE AUTOMATIC DAMPER Filed March 1'7, 1930 Patented May 26, 1931 v UNITED safari-2s PATENT OFFICE WELIAM I). IQUCE, OF EAVERHILL, MASSACHUSETTS, ASSIGNOR F ONE-HALF TO JOSEPH E. DUBE, 0F HAVERHILL, MASSACHUSETTS AUTOMATIC DAMPER Application filed march 17, 1930. Serial No. 436,323. 1

This invention relates to certain improvements in dampers which are primarily designed for use in connection with domestic heating furnaces, although adapted for use .5 in larger fuel burning plants.

In the'operation 0 oil burners in domestic furnaces, thermostatic control is usually employed, which acts to shut of]? the burner completely when a certain room temperature is attained, and then to turn the burner on to the fullest extent when the room temperature'i's loweredto another point, so that the burner is either operating to its full capacity, 1 or is completely shut off. In

View ofthe fact that ample provision for the supply of air to the burner, when in operation, must be made, in many installations the air inletis constantly kept open,

so that, after the burner is turned ofi, air will continue to pass up through the burner chamber and boiler and out through the chimney. This constant circulation of relatively cool air through the furnace not only carries away all the heated gases within the same, but has a marked cooling effect on the furnace walls and consequently on the heated air or water which it contains, and, where the air is supplied from the room in which the furnace is located, the heated air in'the room will be drawn up through the chimney and, consequently, cold air from outside will be drawn into the room, resulting in a marked cooling effect on the buildmg.

With a coal burning furnace, the action is somewhat similar, particularly when forced draft is employed, althou heat loss due to the suction action of the chimney is usually somewhat less, as the air inlet to the furnace is usually controlled,

but it is customary, particularly where automatic draft control is employed, to provide an air inlet check, which admits air to the smoke pipe from the room, and this results in drawing warm air from the room and, consequently, cool air into the room from outside, with consequent loss of heat.

While various devices have been produced in an attempt to avoid the loss of heat by the escape of heated air up the chimney in h ordinarily the g be the manner above referred to, these devices,

so far as I am aware, have been either ineffective, or objectionably complicated.

The objects of my invention are to provide a device for automatically controlling the suction action of the chimney to which a furnace is connected, so that the smoke pipe will at no time be openedto a greater extent than is necessary to permit the escape of. burning gases from the furnace, 'but which will not obstruct suchncscape to an extent sufiicient to cause such gases to escape into the roomv in which the furnace is located, which is of simple construction and adapted to be manufactured at small expense, as compared with other devices for the purpose, and is adapted to be readily f a more rapid rate than that at which they would be normally discharged therefrom, to permit the escape of the products of combustion, the external air pressure will cause the passage through the smoke pipe tobe reduced correspondingly, so that the withdrawal of warm-air from the furnace room and a more rapid circulation through the furnace than is necessary for the dischar e of the products of combustion therein will revented.

or a more complete disclosure of the invention, reference is made to the following specification in connectionwith the accompanying drawin s in which t Fig. 1 is a si e elevation indlcattng the manner in which a damper, embodying the invention, is installed. a I Fig. 2 isa top plan view of the damper.

Figs. 3 and at are horizontal, central sectional views thereof taken at line ct-a of Fig. 1 and showing the parts in different positions. I

Fig. 5 is a cross sectional view, at line Fig. 7 is a detail view of a stop which may be employed to limit the closing movement of the damper.

In the drawing a furnace 1, and a chimney or stack 2 are indicated, and are shown as connected. by a'cylindrical smoke pipe 3 which extends approximately horizontally,

the particular embodiment of the invention shown being designed to be inserted between two sections of the smoke pipe and comabout the axis of the plate may swmgfreely. Said plate '9 is tions of the smoke prises a smoke pipe section 4, adapted to be thus interposed.

According to my invention, approximately one half of the section 1 is cut away between its ends, leaving cylindrical end portions adapted for connection with the sec.-

ipe 3. The opening formed in the side 0? thepipe section 4 is preferably included by a vertical lane which bisects the pipe longitudinal and two vertical planes which are disposed at right angles to the longitudinal plane and terminat e therein.

The openin thus formed is enclosed by a casing whic is connected to the pipe section 4 about said-opening and com rises a top wall 5, bottom wall 6, both 0 which are disposed horizontally, and end walls 7 and 8 which extend vertically between the top and bottom walls so that the entrance to the opening in the side of the pipe is square, or rectangular and is enclosed by horizontal and vertical walls.

A damper is provided which is adapted to close said. opening in all positions thereof and which comprises a rectangular shaped sheet meal plate 9, the width of which corres onds' to the distance between the top an bottom walls 5 and 6 and-the length of which to the distance between the side walls 7 and 8, sothat it may be held in a position to close saidopening. Said plate 9 1s rigidly connectedat one end to ametal shaft 10,

which is mounted for rotation between a pair of pivot screws 11, threaded in brackets 110, secured to the top and bottom. walls 5 and 6, in close proximity to the sidewall 7, the ends of saidscrews being conically formed to en age with the ends of said shaft in conica l recesses therein at its axial line, so that the form step, or thrust. bearings therefor; he plate 9 is thus permitted to swing horizontally with minimum friction shaft 10. The width of plate 9 is as nearlyequal as ractlcal to the distance between the top an bottom walls. 5 and 6 and said screws 11 are so adjusted that the edges of the plate are held m close proximity to said walls, but with.- out actual contact therewith, so that the swingin action of the plate will not be.

impede By means of this construction the rectangularly shaped opening enclosed by the Walls 5, 6, 7, and 8 will be practically closed by plate 9 and its extension 12 in all ositions of the plate, which is arrange to swing from a position, in which it extends obliquely inward to approximately the middle of the pi e section .4, and; closes approximately onealf the passageway through said section, as shown in Fig. 4:, to a com pletely open position, in which it is held in parallel relation to the lon 'tudinal central line of the pipe section, as s own in F1 .3-

The damper plate 9 is also provide with an extension 14, which is securedto the-inner side of the plate 9 and extends obliquely inward-therefrom, the inner edge of said ex,- tension being so formed that when the late 9 is in its innermost position, the edge 0 the e tension 14; will-engage the inner surface of the pipe section, so that the plate 9 and its extension 14 will practically completely close the passageway throu h the pipe section, it being understood t at even in the closed tion Wlll ordinarily and preferably permit a slight leaka e past the same.

An arm 15 1S rigidly mounted on the late osition of these parts the construc-' 9 and arranged to extend horizontallyt erefrom in opposite relation thereto axis and a counter weight 16 is ad ustably mounted on said arm.

between 'the adjacent sections of the smoke pipe it is preferably so. set thatthe axial line pastsits When the section 4 is placed in position the gravity of the plate 9 and its extensions 6 12 and 14 tend to cause said plate to swing to its open position. This bias to swing to open. position is counter balanced bythe weight 16, which is adjusted to compensate for inaccuracies in setting up,so that the swinging movement of the damper may be practically unaffected by gravity. How'- ever, as a matter of safety it is considered preferably to adjust the weight so as to have the'damper biased slightly to open by gravity, so that when the plate!) is acted on by ravity only, it will swin to open position, ut.any slight action'ten ing 1'40 SWmg'it in to the closed positionthe opposite direction will cause it to swing The outward swinging movement to open position may be limited by any suitable stop, but as constructed, the extension 14 will e11- gage the inner side of the pipe section 4 and act as a stop to limit this outward movement. The inward movement may be limited by the engagement of the damper or plate extension 14 with the inner side of pipe 4, or by the engagement of a lip 120 on the extension 12, or a set screw 18 therein, with the lip 80 on the wall ,8. A look may be provided toprevent movement of the plate 9 in either direction, the locking means shown consisting of a latch or do 17 mounted on the wall 8 near its outer e ge and arranged to engagekany one of a series of notches in the top edge of the plate extension 12, this being. employed only when the automatic operation of the devlce is not desired.

With the above described construction, while the damper is, as before stated, preferably so balanced thatthe action of gravity tends slightly to swing it to the open position, it will be understood that but a slight force is required to swing it to closed position and hold it in this position. Also that, by pivoting the damper atone side of the passage which it is adapted to close and arrangingit so that it extends towards the outlet from its axis and swings towards the inlet as .itcloses to a position in which it extends obliquely across the passage, in the direction of the normal flow of gas therethrough, from its axis, the damper will be adapted to act as a check valve, as gas forced from the furnace against the adjacent or inner side of plate 9 and extension 14 will tend to swing the damper to open position, while gas forced in the opposite direction, or down the chimney will tend to swing it'to closed position, so that'down draft past the damper will be prevented. Furthermore, if there is a suction action at the discharge end of the pipe 4 which reduces the pressure at the in- V Under normal conditions the operation of b flow of highly let end thereof below atmospheric pressure, the atmospheric-pressure on the outer side of plate 9 of the damper will act to move the damper towards its closed position, until these pressures are equalized.

the damper is as follows: If the damper is employed in connection with an oil burning furnace, in which the burner is operated at intervals when the burner is not operating, the pressure on the damper will usually act, for reasons hereinafter explained, to .hold it in closed or nearly closedposition. Under suchconditions, when' the burner is lighted, there will immediately be a stron upward heated gas into the smoke pipe and consequently. a rapid increase of pressure against the inner, or furnaceside of the damper plate 9 and its extension 14,

rapidly up the chimney,

, the opposite sides thereof, which are holding the damper in closed position, this pressure being principally the atmospheric pressure on the outer side of plate; 9, thereby immediately forcing the damper to swing to its fully open position and permitting all pro.- ducts of combustion from the furnace to escape freely through the smoke pipe and up the chimney. These conditions will obtain so long as the burner is-in operation, and will cause a heated column so that, when the burner isshut off and the pressureat the furnace side of the damper returns to normal, this rising column of gas will immediately cause a strong suction-action in the, smoke pipe, and will, unless prevented, draw cool air from the air inlet .to the burner up through the furnace, and smoke pipe to the chimney. The suction action of the chimney will, however, at once cause the pressurein the smoke pipe to be lowered below atmospheric pressure, so that, as the outer surface of the damper plate 9 is constantly subjected to full atmospheric pressure, the pressure on the outer side ofthe plate will overbalance the pressure on its inner side and will cause it to swing inward until the pressure from the furnace against the inner side of the plate 9 and its extension 14 equals the inward pressure of the atmosphere on the outer side of the plate. As a result practi cally all the suction action of the chimney on the furnace will be counter-balanced by the inward atmospheric pressure. on the damper, so that the damper will prevent this suction action from causing circulation through the furnace to a material extent. The withdrawal'of the hot air in the furnace will thus not only be. largely prevented] but, what is more important, the continued circulation of coolair through the furnace; by the chimney draft, while the burner is not operating will be almost wholly preof gas to pass vented thereby preventing a substantial loss of heat. Ordinarily the slight leakage past the damper, when in fully closed position,

which preferably is permitted, is' sufiicient to permit the escapeof products of combustion from the usual'pilot flame which is kept building up of pressure at the furnace si e of the damper W111 cause the damper to be opened sufiiciently to per-- mit the escape of sufficient .air or gas. to

equalize the pressure.

urnin but an Ordinarily the suc- 1 tion action of the chimney, when the burner is not being operated, will be'sufiicient to 1 cause the damper to be held in closed, or a nearly closed position.

With. a coal burning furnace, the operation will be somewhat difierent, although in principle, it will be the same. Thatis, with.-

such a furnace the escape of heated gas is much morenearly uniform, so that a con door of the furnace is opened, the pressure at the furnace side of the damper will be increased, causing the damper to be opened, and when the draft is closed the damper will be closed b the external air pressure thereon, as before described, and the suction action of the chimney, when not desired, will be neutralized. The effect produced by opening an air check in the smoke pipe will thus be secured, without causing warm air to be drawn from the room in which the fur- .nace is located, resulting in the prevention opening, whic passage at this point of loss of heat. The cross sectional area of the smoke pipe will thus be automatically maintained at a point sufficient to permit the escape of the products of combustion without substantially impeding the draft action of the furnace and, by adjusting the counter weight 16 on the damper, so that the damper will be opened by gravity when the pressure in the smoke pipe is raised to, or above atmospheric pressure, any retarding action on the draft, when open, may be prevented.

The ratio between the cross sectional area of the smoke ipe and the area of the side is constantly closed by the damper plate 9 and its extension 12, may be varied according to conditions, but ordinarily the area of the side opening will be made somewhat greater than the area of the smoke pipe. The effect of the difference in these areas may however be increased, wholly neutralized, or reversed by adjusting the counter-weight 16.

It will be understood that, while the smoke passage opposite the damper is shown as semi-cylindrical in cross section, the entire may be made rectangu-. lar in cross section, in which case the form of the damper extension 14 will be correspondingly changed. Also," while the principles involved may be embodied in a construction which would operate in positions comprisinga therethru, adapted for connection at its 111- other than that shown, distinct advantages are secured by arranging the damper to swing about an a proximately vertical axis, as the counter-ha ancing of the damper, so that practically the same force will be require to swing-it in either direction in all positions, may be more easily accomplished than under any other conditions of which I am at present awar Various other changes may obviously be made without departing from the spirit and scope of thednvention.

Iclaim: 1. An automatic damper casing having a smoke passage for a furnace and to the pressure at the inlet end of the passage on its inner side in all positions thereof, to permit said plate to be moved inwardly, or outwardly according to which of the pressures thereon over-balances the other, and means arranged to be actuated by said plate to close said passage as the plate is moved inwardly.

2. An automatic damper fora furnace comprising a casing having a smoke passage therethru adapted for connection at'its inlet end to the furnace and it its outlet end to a chimney, and having a side opening to said passage between its ends, a damper plate arranged to swing freely inwardly and outwardly within said side opening and to close said openingand to be approximately balanced against the action of gravity in all positions thereof, and means 3. An automatic damper for a furnace.

comprising a casing having a smoke passage therethrough adapted for connection at its inlet end to the furnace and at its outlet end to a chimney, and having a side opening to said passage between the ends thereof, a. damper plate arranged to be freely moved inwardly and outwardly in said side opening, and to close said opening and to be constantly subjected to atmospheric pressure on its outer side and to the pressure at theinlet end of said passage at its inner side in all. ositions thereof, and means carried by said plate arranged to reduce the transverse area of the passage as the plate is moved inwardly to permit said area to be varied according to the relative pressures on the opposite sides of said plate.

4. An automatic damper for a furnace comprising a casing having a smoke passage therethrough adapted for connection at' its inlet end to the furnace and at its outlet end to a chimney and having a side opening to said passage between itsends, a damper plate mounted to swing freely inwardly and lit . plate, and

' remote from its axis arranged to close operating with the sides of said opening, to c ose the opening in all positions of the means extending from the'plate said passage as thexplate swin s inwardly, the opposite movements of sai plate being approximately balanced against the. action of gravity, to permit the same tobe automatically positloned according to the relative.

pressures against its outer and inner sides. 5. An automatic damper for a furnace comprising a casing having a smoke passage therethrough adapted for connection at its inlet end to the furnace and at its outlet end to a chimney, and having a side opening to said passage between its ends, a

'damper plate mounted to. swing inwardly and outwardly, within said opening about an approximately verticalaxis located adja'cent the sides of said opening next the inlet end of said passage and arranged to close said passage as it swings inwardly,

and means on said plate cooperating with the sides of said opening and arranged to close the opening in all positions of the plate.

- 6. An automatic damper for a furnace comprising a casing having a smoke passage therethrough adapted for connection at its inlet end the furnace and at its outlet end to a chimney, and having a side opening to said passage between its ends, a

' tion with the damper plate arranged to swing freely horizontally inward'and outward within said 1 opening and towards the inlet end of said passage, to close the passage as it swings inward, cooperating means on said plate and on the sides of saidopening to prevent the passage of air through said opening to the passage on'all ositions of the plate and to permit the position of the plate to be controlled according to the relative pressures on its outer and its inner sides.

7. An automatic damper for a furnace comprising .a casing having a smoke passage therethrough adapted for connection at its inlet end to the furnace and at its outlet end to a chimney, and having'a side opening to adamper on said casing to swing horizontally about an axis in proximity to. the side of-said opening next said inlet end from a position in which it closes said opening and permits full opening of said passage to a position in which it closes said passage, the top and bottom sides being extended inward in proximity'to the path of movement of the correspondin edges of said plate and the free end of said plate having an extension cylindrically curved about said axis'in cooperating relaadjacent side of said opening, to close said opening in all inner positions of the'plate, whereby the extent to which the passage is closed wilI be varied accerdof said openinging to the relative pressure on the inner and outer sides of said plate. i

8. An automatic damperfor a furnace comprising a casing having a smoke passa e therethrough adapted for connection at its inlet end to the furnace and at its outlet end to a chimney, and having a side 0 ening to said passage between its ends, sai opening having horizontally disposed top and bottom walls and upright end walls, a damper plate mounted to swing about a vertically disposed axis arranged in proximity to the end walls next the lnlet end of said passage with its top and bottom ed es in proximity to said top and bottom wa ls respectively and having an outwardl projecting extension at its oppositeen from its pivoted end provided with a face formed cylindrically about said axis and arranged to beheld in proximity to the end wall opposite said axis, to close said opening in all positions of said plate, and a assage restricting plate cooperating wit and extending from saiddamper plate -begond said extension in position to close sai passage when said damper plate isiswunginto said passage to an oblique position with relation to the direction of the passage, to permit unbalanced pressure at the inlet end of the passage to force said plate outwardly to open the anced pressure on the outer si of said plate to force the plate inward.

comprising a casing. aving a smoke passage therethru adapted for connection at its inlet end to the furnace and at its outlet end to a chimney, and having a side opening to said passage between its ends, a dam er plate mounted to swing within said opening and across said passa e about a.

opening next the inlet end of said passage, between a position in which it closes said passage and a position in which the passage is open, an arm mounted on said plate and extending horizontally therefrom and o .positely thereto with relation to said axls, a weight adj ustably mounted on said arm to counter balance thegravityaetion on said plate when theaxis is slightlyinclined from the vertical, and means on said plate cooperating with the walls of said opening to close the opening in all positions of said plate, to permit the plate to be positioned accordin to the relative. pressures on the inner an outer sides thereof. v

10. An automatic damper for a furnace comprising a casing having a smoke passage therethrough, adapted for connection at its inlet end to the furnace and at its outlet end to a chimney, andhaving a side opening to said passage and to dpermit unbalpassage between its ends, a,

vertically disposed axis at the-side of said damper plate mounted to swing horizontally i within said opening and across said passage about an axis located in proximity to the side of saidopening next the inlet end of said passa e and slightly inclinedfrom the vertical, w ereby the p ate is biased to be swung by the action of gravity thereon from a posltion in which it c oses said passage to V a position in which the passage is open, an arm connected to said plate and extending horizontally at the opposite side of said axis therefrom, a counter-weight adjustably' mounted on said arm to counter-balance the gravity action on said plate, andmeans on said plate cooperating with the walls of said opening to close said opening in all positions 0 said plate, to permit the late to be positioned according to the re ative pressures on its outer and its inner sides.

In testimony whereof, I have signed my name to this specification. WILLIAM D. LUCE. 

